Short-Term Test Results:
Transitional Housing Energy
Efficiency Retrofit in the HotHumid Climate
Karen Sutherland and Eric Martin
BA-PIRC/Florida Solar Energy Center
February 2013
NOTICE
This report was prepared as an account of work sponsored by an agency of the
United States government. Neither the United States government nor any agency
thereof, nor any of their employees, subcontractors, or affiliated partners makes any
warranty, express or implied, or assumes any legal liability or responsibility for the
accuracy, completeness, or usefulness of any information, apparatus, product, or
process disclosed, or represents that its use would not infringe privately owned rights.
Reference herein to any specific commercial product, process, or service by trade
name, trademark, manufacturer, or otherwise does not necessarily constitute or imply
its endorsement, recommendation, or favoring by the United States government or
any agency thereof. The views and opinions of authors expressed herein do not
necessarily state or reflect those of the United States government or any agency
thereof.
Available electronically at http://www.osti.gov/bridge
Available for a processing fee to U.S. Department of Energy
and its contractors, in paper, from:
U.S. Department of Energy
Office of Scientific and Technical Information
P.O. Box 62
Oak Ridge, TN 37831-0062
phone: 865.576.8401
fax: 865.576.5728
email: mailto:reports@adonis.osti.gov
Available for sale to the public, in paper, from:
U.S. Department of Commerce
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
phone: 800.553.6847
fax: 703.605.6900
email: orders@ntis.fedworld.gov
online ordering: http://www.ntis.gov/ordering.htm
Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste
Short-Term Test Results: Transitional Housing Energy Efficiency
Retrofit in the Hot-Humid Climate
Prepared for:
The National Renewable Energy Laboratory
On behalf of the U.S. Department of Energy’s Building America Program
Office of Energy Efficiency and Renewable Energy
15013 Denver West Parkway
Golden, CO 80401
NREL Contract No. DE-AC36-08GO28308
Prepared by:
Karen Sutherland and Eric Martin
BA-PIRC/Florida Solar Energy Center
1679 Clearlake Road, Cocoa, FL 32922
NREL Technical Monitor: Stacey Rothgeb
Prepared under Subcontract No. KNDJ-0-40339-00
February 2013
iii
[This page left blank]
iv
Contents
List of Figures ............................................................................................................................................ vi
List of Tables .............................................................................................................................................. vi
Definitions .................................................................................................................................................. vii
Executive Summary ................................................................................................................................. viii
Acknowledgments ..................................................................................................................................... ix
1 Introduction ........................................................................................................................................... 1
2 Pre-Retrofit Energy Efficiency Characteristics and Retrofit Plans ................................................ 5
3
4
5
2.1 Building Thermal Envelope .................................................................................................5
2.2 Building Airtightness and Ventilation .................................................................................6
2.3 Mechanical Space Conditioning System .............................................................................6
2.4 Water Heating System .........................................................................................................7
2.5 Lighting, Appliances, and Miscellaneous Loads .................................................................7
Pre-Retrofit Analysis ............................................................................................................................ 9
3.1 Utility Data Analysis............................................................................................................9
3.2 Simulation Development ...................................................................................................12
3.3 Simulation True-Up ...........................................................................................................13
3.4 Proposed Retrofit ...............................................................................................................15
Characteristics of Post-Retrofit Energy Improvements ................................................................. 20
4.1 Attic Insulation and Duct Locations ..................................................................................20
4.2 Windows ............................................................................................................................21
4.3 Whole House Infiltration ...................................................................................................21
4.4 Heating, Cooling, and Air Distribution Systems ...............................................................22
4.5 Water Heating System .......................................................................................................23
4.6 Lighting and Appliances ....................................................................................................24
Post-Retrofit Energy Cost Savings and Cost Effectiveness .......................................................... 25
5.1 Measure Cost Savings and Cost Effectiveness ..................................................................27
5.2 Summary of Cost Effectiveness .........................................................................................28
6 Conclusions ........................................................................................................................................ 29
References ................................................................................................................................................. 31
Appendix: SIR Calculation Assumptions ............................................................................................... 32
v
List of Figures
Figure 1. The Beacon House, transitional men’s housing shelter in St. Petersburg, Florida, built in
1926 ........................................................................................................................................................ 1
Figure 2. Number of existing multifamily housing units in the southern United States, by decade.. 3
Figure 3. Eaves and vented attic of the Beacon House .......................................................................... 5
Figure 4. One of two through-the-wall exhaust fans ventilating the kitchen ........................................ 6
Figure 5. Natural gas furnace (left); window AC unit, fitted into rough opening with cardboard and
foam (right) ............................................................................................................................................ 7
Figure 6. The commercial kitchen (refrigerators, left; range, right) feeds approximately 200 people
each night .............................................................................................................................................. 8
Figure 7. Actual and predicted electricity use by CDD. Y-intercept (base load) at 6,551 kWh. ........ 10
Figure 8. Actual and predicted natural use by HDD. Y-intercept (base load) at 65 therms. ............. 11
Figure 9. Utility costs disaggregated by heating, base therms, cooling, and base kWh .................. 11
Figure 10. Actual versus TMY3 weather-normalized annual energy costs; changes occur in
cooling and heating use only ............................................................................................................ 12
Figure 11. Disaggregated cooling, heating, kWh base load, and therms base load (range) ............ 13
Figure 12. Normalized actual versus simulated monthly energy use. A dip in February simulation
therms (purple) results from a warm climate with few HDDs, which is sensitive to localized
weather patterns. ................................................................................................................................ 15
Figure 13. Post-retrofit, researchers observed an airflow pathway from a large open wall cavity
between the AHU and the filter grille ................................................................................................ 22
Figure 14. Post-retrofit ground floor, SEER 15 heat pump AHU .......................................................... 22
Figure 15. Two externally mounted gas tankless water heaters .......................................................... 24
Unless otherwise indicated, all figures were created by the BA-PIRC team.
List of Tables
Table 1. Sample Utility Billing Periods Used to Estimate Monthly Consumption ................................ 9
Table 2. Proposed Retrofit Package and Predicted Annual Energy Cost Savingsa ........................... 16
Table 3. Post-Retrofit Findings by Measurea.......................................................................................... 20
Table 4. Post-Retrofit Measure and Package Costs and Savingsa ...................................................... 26
Unless otherwise indicated, all tables were created by the BA-PIRC team.
vi
Definitions
AFUE
Annual fuel utilization efficiency
AC
Air conditioning
ACH50
Air changes per hour when a house is depressurized to negative 50
Pascals
AHU
Air handling unit
BA-PIRC
Building America Industrialized Housing Partnership
CDD
Cooling degree days
CFL
Compact fluorescent lamp
CFM
Cubic feet per minute
DOE-2
An energy use perdition software developed by James J. Hirsch &
Associates in collaboration with Lawrence Berkeley National
Laboratory
EER
Energy efficiency ratio
EF
Efficiency factor
EGUSA
Energy Gauge USA
HDD
Heating degree days
HSPF
Heating seasonal performance factor
kWh
Kilowatt hour
Pa
Pascal
R-value
Value denoting thermal resistance
RESNET
Residential Energy Services Network
SEER
Seasonal energy efficiency ratio
SHGC
Solar heat gain coefficient
SIR
Savings to investment ratio
TMY3
Typical Meteorological Year 3
Qn,out
Normalized duct system leakage to the outside; a measurement of duct
leakage to non-conditioned space at test pressure of negative 25
Pascals divided by the conditioned floor area
R2
R-squared, coefficient of determination
U-value
Value denoting thermal conductance
vii
Executive Summary
This project evaluates the renovation of a 5,800-ft2, multiuse facility located in St. Petersburg, on
the west coast of central Florida, in the hot-humid climate. An optimal package of retrofit
measures was designed to deliver 30%–40% annual energy cost savings for this building with
annual utility bills exceeding $16,000 and high base load consumption. Researchers projected
energy cost savings for potential retrofit measures based on pre-retrofit findings and
disaggregated, weather-normalized utility data. A cost-benefit analysis was conducted for the
seven retrofit measures implemented; adding attic insulation and sealing soffits, tinting windows,
improving whole-building airtightness, upgrading heating and cooling systems and retrofitting
the air distribution system, replacing water heating systems, retrofitting lighting, and replacing
laundry equipment.
Based on additional data collected from a post-retrofit audit, the projected energy cost savings
for the full retrofit package are 35%; projected annual energy cost savings are $5,375.
Projections using full measure costs indicate that the lighting retrofit and window film measures
yield the highest savings to investment ratios. However, when considering only incremental
costs, the high-efficiency heating and air conditioning systems presented the strongest savings to
investment ratio.
The building’s architectural characteristics, vintage, and occupancy profile presented challenges
from a simulation perspective and from an audit/data collection perspective to optimize a retrofit
measure package and resulting economic projection. This report addresses these challenges in an
effort to assist contractors and energy auditors implementing deep-energy retrofits in structures
with characteristics that are similar to the subject building. The report also includes a true-up
methodology that aligns pre-retrofit utility data with simulation weather data, a technique that is
useful for modeling energy efficiency retrofits in general.
viii
Acknowledgments
The authors gratefully acknowledge the U.S. Department of Energy, Office of Energy Efficiency
and Renewable Energy, which sponsored this work under the Building America Program.
The authors wish to thank Ken Fonorow, the certified home energy rater who conducted the
energy audits. We also appreciate the cooperation and support of our industry partner in this
work, Sam Moore with Matrix Construction, without whom this research would not have been
conducted. We are also grateful to the staff and residents of the Free Clinic Beacon House,
specifically Yolanda Giovannetti, and its parent organization, the St. Petersburg Free Clinic, Inc.,
for providing the research building and for their cooperation and input.
We also express great appreciation to the Florida Solar Energy Center’s Danny Parker, who
provided energy modeling consultation, Janet McIlvaine who gave technical guidance, and
Danielle Daniel for her excellent editorial assistance.
ix
1 Introduction
Free Clinic Beacon House, hereafter referred to as the Beacon House (see Figure 1), is owned
and operated by St. Petersburg Free Clinic, Inc., 1 a multiuse facility that provides transitional
shelter to homeless men. The shelter can sleep and feed up to 30 men and provides community
evening meals for approximately 200 people every day. The facility also provides its residents
with bathing, laundry, and dining accommodations. A large commercial kitchen allows for food
storage and preparation for the community meal services.
Figure 1. The Beacon House, transitional men’s housing shelter in
St. Petersburg, Florida, built in 1926
Constructed in 1926, the concrete block, two-story building comprises approximately 5,800 ft2 of
conditioned and semiconditioned space with a flat, vented, gravel roof. The building’s kitchen is
not conditioned or isolated from the rest of the building with an air/thermal barrier. The first
floor houses an office, two bathrooms, a dining area, a serving area, a kitchen, a general
assembly area, and a laundry room. The second floor consists of two offices, four semiprivate
rooms, a large dormitory with 28 bunk beds, and two bathroom areas containing several sinks,
toilets, and showers.
The unique characteristics of the home include high occupancy with respect to living area
(occupant density), frequent movement of residents and staff in and out of the building,
dissimilar resident sleep patterns (approximately 25% of their residents work an evening or a
night shift), three commercial offices shared by three full-time and two part-time staff members,
and a commercial kitchen operating throughout most of the day. The clinic administration targets
residents who will have minimum six-month tenures; occasionally, however, emergency referrals
are taken in from local shelters.
Reported annual utility costs for the mixed-fuel building exceed $16,000 (approximately $14,000
for electricity and $2,000 for natural gas). The natural gas fuels two space heating furnaces and a
commercial range.
1
http://www.stpetersburgfreeclinic.org/
1
Driven to reduce operational costs, the Beacon House sought grant funding to renovate the
building. In addition to being expensive to run, the staff described building temperature and
humidity as difficult to control. Funding to retrofit the building came from HomeAid, 2 a
nonprofit organization that has partnered with the Walmart Foundation to create an
Environmental Sustainability Program that is designed to integrate environmental sustainability
into shelter development. Its target metrics are to reduce total annual utility costs by 40% and
recover retrofit costs within five years. The Beacon House staff members are excited about
reducing their energy use, as any operational cost savings will be directed toward such things as
medical treatment, transportation, and job interviewing skills development for the population
served by its umbrella organization, the St. Petersburg Free Clinic.
The St. Petersburg Free Clinic contracted with Matrix Construction, Inc., hereafter referred to as
Matrix, as general contractor for the Beacon House retrofit. Technical assistance in designing a
retrofit package aimed at meeting the goals of Beacon House and the funding program’s target
metrics was provided by the Building America Partnership for Improved Residential
Construction (BA-PIRC), which predicted savings and calculated paybacks for various energy
conservation strategies.
Building performance modeling based on a low-level pre-retrofit energy audit was conducted
with Energy Gauge USA (EGUSA) (Florida Solar Energy Center 1996–2005), a DOE-2 based
hourly home energy use simulation software program. Thermal envelope measurements and
characteristics, and equipment features and locations were documented during the audit for the
simulation input. A model based on the pre-retrofit audit was used in conjunction with actual
utility data to construct a baseline simulation model from which to run parametric analyses to
predict energy cost savings for different features and components.
To secure funding for the retrofit, an initial cost-benefit analysis was conducted for each
proposed measure and for the proposed retrofit package as a whole to present to the funding
agency. Matrix provided retrofit cost estimates based on subcontractor bids. For each proposed
measure and for the retrofit package as a whole, projected annual energy cost savings were
divided by associated retrofit costs to estimate simple payback, a metric established by the
funding organization.
A post-retrofit energy audit was conducted, including blower door and duct blaster tests to
measure whole-building and mechanical distribution system leakage. A revised energy use
simulation based on the post-retrofit audit was compared to the pre-retrofit baseline model to
predict energy cost savings for completed measures and the overall retrofit package. Post-retrofit
interviews with Matrix and the Beacon House administration provided insights into the
renovation process from contractor and occupant perspectives.
Actual contractor costs were not available as of December 2012; thus, original subcontractor bids
were used as input for post-retrofit cost-effectiveness analyses. In addition to calculating the
simple payback according to the funding organization’s metrics, researchers calculated savings
to investment ratio (SIR). In follow-up to the retrofit, the Beacon House will provide HomeAid
copies of its utility data for 12 months following the renovation.
2
http://www.homeaid.org/About-Us
2
Findings from this research may have broader applicability to multifamily retrofits of similar
vintage. Multifamily building census data for the southern United States are referenced as an
approximation for dwellings in the hot-humid climate. Figure 2 plots housing units by decade
and shows that older vintage housing structures with 5 to 49 units abound in the southern region.
As of the 2000 U.S. Census (Residential Finance Survey 2001: Census 2000 Special Reports
2005), approximately 25 million multifamily housing properties with 5 to 49 units were built
before 1960 in the southern region of the United States.
Figure 2. Number of existing multifamily housing units in the southern United States, by decade
This study has more specific relevance to retrofits of shared-use facilities such as transitional
housing, dormitories, and assisted living facilities, which are partially commercial given the
services provided. According to the U.S. Census Bureau, there were 3,434 temporary shelters
nationwide, as of 2002 (Industry Statistics Sampler: NAICS 624221 Temporary Shelters 2002).
Among these, 635 structures are located in southern states in the hot-humid climate region:
Texas, Florida, Georgia, South Carolina, Alabama, Louisiana, and Mississippi. Transitional
shelters conducting high performance retrofits not only improve occupant comfort and structure
durability. By reducing building operating costs, the providers benefit from lower monthly
electricity and natural gas expenses, thereby freeing funds to enhance delivery services.
Energy conservation measures that focus on cost-effective approaches for multifamily housing
retrofits are well documented (Brozyna 2012, for example); however, research specific to the
unique attributes of shared-use facilities is scarce in the literature. This report answers the
following questions in an effort to help contractors and energy auditors overcome the challenges
of implementing deep-energy retrofits in structures with similar characteristics to the subject
building.
3
•
What potential obstacles are presented in evaluating energy use in a building with these
architectural and operational characteristics?
•
What possible difficulties are presented in retrofitting a transitional housing building with
these architectural characteristics and of this vintage?
•
What measures may provide the best projected energy cost savings and SIRs in a facility
with similar characteristics and services?
4
2 Pre-Retrofit Energy Efficiency Characteristics and
Retrofit Plans
In September 2011, researchers conducted a low-level energy audit of the Beacon House.
Following is a summary of the building’s components, highlighting energy efficiency parameters
used in simulation modeling.
2.1 Building Thermal Envelope
Medium-colored tar and gravel covered the decking of the building’s built-up flat roof, which
had an estimated surface solar absorptance of 0.75. The vented attic with 2-ft eaves is presented
in Figure 3. The attic depth and insulation value could not be visually inspected during the preretrofit energy audit because the attic was not accessible, and the scope of the low-level energy
audit did not permit destructive investigation. It may have been possible to use a small scope or
viewer, but the level of insulation was expected to be so variable that ascertaining an average
would have been difficult. The location of the internal attic hatch was in a precarious place and
external access would have required that the permanently affixed soffit be removed and a
mechanism installed to elevate the auditor 20+ ft. Based on conversations with the contractor, an
attic insulation R-value of 1 was used for modeling purposes.
Figure 3. Eaves and vented attic of the Beacon House
The 60 ft × 48 ft building consisted of four exterior concrete block walls, void of insulation or
stucco finish. Exterior walls were painted a light color, and an estimated solar absorptance of
0.50 was used for modeling purposes.
The 44 windows were clear, single-pane, aluminum-framed glass in various states of disrepair.
Assumed efficiency for all windows was a U-value of 1.20 and a solar heat gain coefficient
(SHGC) of 0.80. The 2-ft soffit overhang provided shading for the east- and west-facing
windows; the second-story south-facing windows were shaded by awnings. There were five
entrance doors, three insulated with a presumed U-value 0.46, one insulated with a presumed Uvalue of 0.20, and one glass door. The exterior doors provided opportunities for airtightness
through improved weather stripping.
The floor forming the thermal envelope was an uninsulated, slab-on-grade foundation finished
with vinyl composition tiles.
5
2.2 Building Airtightness and Ventilation
A primary source of uncontrolled airflow into and out of the building was through the kitchen,
which was ventilated by two built-in exhaust fans (Figure 4). Makeup air was provided by
opening the kitchen’s exterior door. Because the room was not isolated from the rest of the
building, air from the conditioned portions of the building was exhausted through the open
kitchen door and exhaust fans.
Figure 4. One of two through-the-wall exhaust fans ventilating the kitchen
Whole-house airtightness is calculated as air changes per hour (ACH50) measured at a test
pressure of negative 50 Pa with respect to the outside, divided by the building volume.
Researchers were unable to conduct a pre-retrofit whole-building airtightness test, given the
previously described kitchen configuration, and the perception that it could not be depressurized.
For modeling purposes, researchers estimated whole-building leakage of ACH50 = 22 based on
normalized results from previous retrofit work involving measurements in existing buildings of
similar enclosure characteristics and geographic location (McIlvaine 2010). 3
2.3 Mechanical Space Conditioning System
Two 30-year-old, 108,000-Btu natural gas-fueled furnaces (Figure 5) were used to heat the
building and were operated by non-programmable thermostats. The first-floor unit was located in
the entrance hallway and the second system in the second-floor mechanical closet. The
operational efficiencies for both units were unknown and an annual fuel utilization efficiency
(AFUE) of 0.78 was initially used in modeling. The distribution system for the first-floor unit ran
between the original ceiling and the newer dropped ceilings. Researchers felt that the air and
thermal barriers between the vented attic and dropped ceilings (which contained the ducts) were
poor at best; therefore, the pre-retrofit audit indicates the second system’s supply ductwork is in
attic space.
Twenty-two window air conditioning (AC) systems of various operational conditions were used
to cool the entire building. The unknown operational efficiencies were initially modeled to be a
mix of energy efficiency ratios (EERs) 7 and 8. As Figure 5 shows, some AC units were poorly
fitted, creating additional airflow pathways.
3
After pre-retrofit modeling was completed, a tested ACH50 of 28.7 was achieved by masking off kitchen exhaust
fans, proving the original estimate to be conservative.
6
Figure 5. Natural gas furnace (left); window AC unit, fitted into rough opening
with cardboard and foam (right)
Duct airtightness can be measured by depressurizing the duct system with a calibrated “duct
blaster” fan in accordance with a standard test procedure (RESNET 2012). Duct tightness is
expressed in terms of airflow required to achieve a standard test pressure (25 Pa) in the duct
system, measured in cubic feet per minute or CFM25. Leakage involving air to or from
unconditioned spaces or the outside is expressed as CFM25,out, and results normalized by
conditioned floor area of the building yield Qn,out.
The existing ductwork, located between floors and between the dropped ceiling and the original
ceiling below the attic cavity, distributed heat from the gas furnaces. Insulation levels were
unknown, but were conservatively estimated to have an R-value of 6. The pre-retrofit audit did
not include a duct tightness test because the building could not be depressurized, which is
necessary to determine duct leakage to the outside. For modeling purposes, researchers estimated
Qn,out to be 0.22 (McIlvaine 2010).
2.4 Water Heating System
The domestic hot water supply consisted of electric resistance tanks: a 120-gal tank servicing the
six-shower bathroom, a 40-gal tank supplying the kitchen, and a 20-gal tank that serviced the
Americans with Disabilities Act (ADA) accessible bathroom. None of the operational
efficiencies were known. But given their apparent age, an efficiency factor (EF) of 0.80 was
assumed for all three units.
2.5 Lighting, Appliances, and Miscellaneous Loads
Lighting was composed primarily of 4-ft and 8-ft T12 linear fluorescent bulbs with a few
incandescent screw type bulbs. Five ceiling fans, of unknown efficiencies, operated throughout
the building. Software efficiency defaults were used to model the fans.
Multiple commercial-grade refrigerators (Figure 6) with internal compressor and condenser coils
were necessary given the volume of food services. The eight-burner commercial gas stove
(Figure 6) was accompanied by an outdoor-venting range hood. There were two sets of coinoperated washers and dryers, one older set and the other relatively new. Simulation software
default efficiencies were assumed for both sets. The laundry appliances are available to
occupants for personal use and were used twice weekly by facility staff for linens, towels, etc.
7
Figure 6. The commercial kitchen (refrigerators, left; range, right) feeds
approximately 200 people each night
Miscellaneous loads are influenced by seven computers used by staff and six televisions in the
semiprivate rooms and general assembly areas.
8
3 Pre-Retrofit Analysis
In an effort to improve, or true-up pre-retrofit energy use modeling, researchers obtained Beacon
House utility data for one year of pre-retrofit billing. The following information is an account of
the utility data analysis, energy use modeling, and simulation true-up conducted to create a
baseline energy use model to evaluate Beacon House energy cost saving measure projections.
3.1 Utility Data Analysis
Researchers were provided 12 consecutive months of the facility’s utility data spanning from
August 2010 through July 2011 for electricity and September 2010 through August 2011 for
natural gas. To use this data to true-up the pre-retrofit simulation, weather normalization was
necessary to align actual utility data with simulation results that use historical weather data. 4
The first step toward weather normalization was to disaggregate the utility data into energy uses
for cooling, heating, and base load—the amount of energy consumed principally when AC and
heating are not necessary. Disaggregation was conducted with a simple linear regression based
on the best fit between energy use and weather data to separate consumption increases related to
cooling and heating needs. Two regressions were run: one to separate cooling energy use, a
second for heating energy use. The first regression consisted of 12 months of electricity use as
the dependent variable and 12 months of cooling degree days (CDDs) as the independent
variable. The second regression was similar, but it consisted of natural gas consumption and
heating degree days (HDDs) as the independent and dependent variables, respectively.
Monthly weather data were taken from the National Oceanic and Atmospheric Administration’s
“Local Climatological Data Publications” for the St. Petersburg area. 5 Utility billing periods did
not align precisely with each calendar month, so calendar month use estimates were created by
averaging daily use for each billing cycle and summing the averages for all days in a given
month (Table 1). For example, daily averages from the first two billing cycles in Table 1 were
used to estimate the consumption for January 2011 by multiplying “days in current bill” and
“days in previous bill” by their associated average kilowatt hours (kWh)/day, and summing these
products. The kWh estimate for January 2011 is 6,802.
Table 1. Sample Utility Billing Periods Used to Estimate Monthly Consumption
kWh Bill
Start Date
12/15/2010
1/17/2011
2/15/2011
Actual Utility Bill
Billing
kWh Bill Actual
Days
End Date
kWh
in
Cycle
1/7/2011
7,104
33
2/15/2011 6,491
29
3/16/2011 7,269
29
Calendar Month Estimate
Average
kWh/
Day
Month
Days
in
Month
Days in
Current
Bill
Days in
Previous
Bill
kWh/
Month
215
224
251
Dec 10
Jan 11
Feb 11
31
31
28
17
15
14
14
16
14
6,940
6,802
6,643
After the data were organized, the regressions were run. Researchers examined the coefficient of
determination (R2) results to judge the fit of the model to the data. The results from the linear
4
5
EGUSA bases its weather data on Typical Meteorological Year 3 (TMY3) weather data
http://www7.ncdc.noaa.gov/IPS/cd/cd.html
9
regressions, R2 = 0.90 for the electricity model and R2 = 0.98 for the gas model, indicate the
models’ strong predictive values.
An alternative method of estimating utility bills to match the weather periods would be to align
weather data with billing periods. Rather than creating monthly use estimates from daily
averages, researchers investigated reorganizing daily degree day data into categories precisely
matching the utility bill periods. Using daily degree day data removes the error associated with
monthly use averages and undoubtedly improves the prediction model. The nearest location of
available daily degree data was 20 miles away in Tampa. Unfortunately, the weather data for this
location were less similar than researchers hoped. Although daily Tampa data did provide a
slightly better prediction of electricity use, the gas use prediction was degraded. For this study,
researchers opted to proceed with the previously described calendar month use estimates.
Regression results were then used to predict monthly base load, cooling use, and heating use.
The model’s resulting line of best fit provides a y-intercept that represents base load: when CDD
or HDD, and in turn cooling or heating energy use, is zero. Figures 7 and 8 are plots of the actual
and predicted electricity use by CDD and gas use by HDD. For electricity, the constant monthly
base load is where the trend line for the regression plot intercepts the y-axis, at 6,551 kWh. Use
exceeding this threshold is associated with increased CDD and is interpreted as cooling load. The
regression run with natural gas use produced a monthly base load of 65 therms.
Figure 7. Actual and predicted electricity use by CDD. Y-intercept (base load) at 6,551 kWh.
10
Figure 8. Actual and predicted natural use by HDD.
Y-intercept (base load) at 65 therms.
Once cooling and heating use was disaggregated from the base load, monthly use was predicted.
Multiplying the independent variable (CDD or HDD) regression coefficient by the CDD or HDD
value for each month produces monthly cooling and heating energy for the 2010–2011 utility bill
period. Annual base load electricity and natural gas use are 12 times their respective base loads
(y-intercept). Results for the annual total disaggregated energy costs are shown in Figure 9, using
average Florida utility rates. The large proportion of base load electricity is noteworthy: 58% of
annual utility costs and 71% of total electricity use.
Figure 9. Utility costs disaggregated by heating, base therms, cooling, and base kWh
Monthly energy use and cost predictions were then made as if the building had been subject to
Typical Meteorological Year 3 (TMY3) weather data in an effort to align the predictions with
11
simulation results. This time, the independent variable (CDD or HDD) regression coefficients
were multiplied by the TMY3 CDD or HDD value for each month, to yield weather-normalized
results. TMY3 data have 9% fewer CDDs and 37% more HDDs. Therefore, predicted cooling
use declined, and predicted heating use rose under the weather-normalized assumptions. Because
base load estimates were unchanged, the net effect was a decrease in the overall electricity use
and an increase in natural gas use, compared to the actual utility data. Figure 10 provides
comparisons of end-use energy costs when disaggregated using actual weather and TMY3
weather. The next discussion addresses how the disaggregated, weather-normalized monthly
consumption projections were used to true-up the energy use simulation developed in EGUSA.
Figure 10. Actual versus TMY3 weather-normalized annual energy costs;
changes occur in cooling and heating use only
3.2 Simulation Development
Choosing meaningful energy use simulation software for this study was challenging. The Beacon
House, which provides transitional housing and commercial food services, presents residential
and commercial characteristics that posed energy modeling challenges. Researchers chose to
model the building with residential energy simulation software and then modify operational
schedules and assumptions based on utility data, the shelter’s specific set of services, and the
building’s unique characteristics. EGUSA was chosen in part because it provides monthly energy
end-use reports, which were referenced as part of the simulation true-up exercise.
Location, occupancy, geometry, equipment, efficiencies, etc., obtained from the low-level preretrofit audit were initially characterized in the software with typical residential building patterns
and schedules to evaluate pre-retrofit energy use. Results from this simulation are referred to as
Initial Base. There are large discrepancies between the weather-normalized energy use and the
projected energy use of the Initial Base model, which uses standardized residential assumptions.
A comparison of cooling, heating, electricity base load, and natural gas base load (the range)
between these two scenarios is referenced in the first two bars of Figure 11. Given that
occupancy cannot be traditionally defined (housing and feeding 30 residents and serving 200
meals to the community daily) and the atypical building characteristics (a large, nonisolated,
semiconditioned space, and 22 window air conditioners), researchers modified the simulation in
12
an effort to more accurately reflect the unique characteristics of the shelter, referred to as the
True-Up model (see the third bar of Figure 11).
Figure 11. Disaggregated cooling, heating, kWh base load, and therms base load (range)
3.3 Simulation True-Up
The disaggregated and weather-normalized utility data described in Section 3.1 provided a guide
to adjust appliance uses, equipment efficiencies, schedules, and set points used in the simulation
to achieve more accurate results. The simulation’s annual summary energy uses were compared
to the disaggregated, weather-normalized consumption, which provided four targets: cooling
energy, heating energy, electricity base load, and natural gas base load (range).
Consider natural gas consumption first. Using the heating energy projected from the weathernormalized natural gas use as a target, researchers adjusted heating set points and unknown
furnace efficiencies until they found the best fit. The remaining gas base load became the annual
use of the range, the remaining gas-fueled appliance.
Next consider electricity use. Air conditioner efficiencies and cooling set points were similarly
adjusted to produce the cooling energy target derived from the weather-normalized electricity
use. The remaining annual use, the base load electricity consumption (79,000 kWh), needed to be
distributed among the remaining electricity draws—water heating, refrigeration, lighting, fans,
laundry facilities, and miscellaneous loads. Having to apply a great portion of the electricity use
(71%) among these many uses presented a gap in the model and a challenge for researchers.
Software defaults using 25 bedrooms, 6 the HERS 2006 appliance schedule, and software
estimates for domestic hot water use based on 30 occupants fell short of this goal by 54,000
kWh.
6
EGUSA produced unpredictable simulation energy use results when number of bedrooms exceeded 25.
13
Researchers reasoned the water consumption and refrigeration must have been much higher than
defaults, as they are heavily influenced by meal services. Annual water consumption was
projected to be about twice the simulation’s estimated water use for the given occupancy (using
28,000 kWh), and commercial refrigeration was estimated at 10 kWh/day (3,600 kWh/yr).
Lighting was also addressed specifically. Total lighting use was estimated with a bulb inventory
and approximation-of-use hours, yielding 27,500 annual kWh. The balance of yearly electricity
base load, approximately 19,500 kWh, was distributed among ceiling fans, clothes washing and
drying, and miscellaneous loads. A multiplier was applied to the HERS 2006 appliance
schedules for the associated end uses, to raise overall projected total annual base load electricity
consumption 79,000 kWh.
The software simulates whole-house energy use, so altering lighting and appliance schedules
impacts heating and cooling loads; therefore, heating and cooling equipment efficiencies and set
points were readjusted to mimic the target loads determined through the weather normalization.
Thus, an iterative process took place until all four weather-normalized targets were reached.
Heating set points were ultimately set to 73°F and cooling to 82°F; the furnace AFUE was 0.71
and AC window unit efficiencies were a combination of EER 8 and 9. The True-Up model is the
product of these simulation adjustments.
Figure 13 shows the weather-normalized consumption for the Beacon House, as well as the
Initial Base model and True-Up model pre-retrofit simulations, disaggregated by cooling,
heating, electricity base load, and range. The figure reveals how well the True-Up model’s
cooling, heating, and remaining base load uses mimic the weather-normalized utility data.
However, the large purple section of the bars (kWh base load) highlights the model’s inability to
guide consumption for elements that fall within this category: domestic hot water, refrigeration,
lighting, ceiling fan, clothes washer, dryer, and miscellaneous loads.
As a final evaluation of model fit, the weather-normalized and disaggregated utility data were
compared to the True-Up model’s simulated monthly consumption by end use. Figure 12
displays monthly natural gas and electricity use for the weather-normalized data and the True-Up
model. We see good alignment in monthly electricity consumption, varying at most by 13%; the
weather-normalized utility data are slightly higher in the swing season months. The natural gas
use does not match nearly as well for certain months. This is probably because the weather data
used by simulation software actually uses TMY3 data from a nearby, but different location.
These differences are often minor, but in the case of a warm climate with relatively few HDDs, a
localized cold front can create relatively large monthly differences between nearby locations. As
Figure 11 demonstrates, the utility data-backed, weather-normalized simulation clearly provided
researchers a more accurate baseline to project annual energy savings. Figure 12 substantiates the
model’s strength to mimic monthly consumption.
The True-Up model served as the baseline for the post-retrofit cost savings analysis. The
proposed retrofit measures are the subject of the next section.
14
Figure 12. Normalized actual versus simulated monthly energy use. A dip in February simulation
therms (purple) results from a warm climate with few HDDs, which is sensitive to localized
weather patterns.
3.4 Proposed Retrofit
Researchers worked with Matrix to develop the proposed retrofit package estimated to achieve
37% annual energy savings. The package of improvements is summarized in Table 2. Economics
for sets of components appear wherever cost data are combined; e.g., attic insulation and duct
location measures.
Attic Insulation and Duct Locations: Recommendations were to remove the tongue-and-groove
soffit material, then to work from the perimeter and densely pack the attic cavity between the
roof and the dropped ceiling section containing ductwork, with either cellulose or formaldehydefree fiberglass blown-in insulation to achieve an R-value of 38. The proposed retrofit also
included installation of new soffit material and soffit sealing to create a continuous air barrier
around the exterior perimeter. This brought the ducts in the cavity below into conditioned space
to reduce thermal losses. This measure was projected to save $792, or 5.1% of the total annual
bills.
Windows: Window replacement would have been ideal; however, most windows were
operational, and with the extensive termite damage around some windows, the energy savings
possible from this measure would not have supported the cost, according to the grantor’s metrics.
Researchers recommended that a window film with an SHGC no higher than 0.40 be applied to
all windows. A budget-related decision was to forgo applying film to several windows shaded by
trees and overhangs. This measure was projected to save $162 annually, or 1% of the total annual
bills.
15
Table 2. Proposed Retrofit Package and Predicted Annual Energy Cost Savingsa
Components
Pre-Retrofit
Roof
Vented, flat, gravel,
medium color (0.75 solar
absorptance)
Attic
Insulation
Insulated at ceiling (R-1)
Duct
Locations
Exterior
Walls
Windows
Doors
Floors
WholeHouse
Infiltration
Heating and
Cooling
System
System 1: supply, return,
and AHU interior
System 2: supply attic,
return, and AHU interior
Light-colored block walls
(0.50 solar absorptance)
44 single, clear, metal
frame
(U-value = 1.20;
SHGC = 0.80)
3 insulated (U-value = 0.46;
1 insulated (U-value 0.20)
100% vinyl
Compromised envelope
unable to depressurize
(estimated
ACH50 = 22)
No ventilation system
22 window units (19 @
8 EER; 3 @ 9 EER)
2 gas furnaces;
108 kBtu/h
(AFUE = 0.71)
No programmable
thermostat
Proposed Retrofit
Measure
Cost
Estimate
Projected
Annual
Cost
Savingsb
Projected
Percent
Savingsb
Projected
Annual
kWh
Savingsb
Projected
Annual
Therms
Savingsb
Simple
Payback
(Years)
Ceiling insulated to
R-38
$5,600
$792
5.1%
4,440
130
7
Tint all south- and
east-facing windows
to SHGC ≤ 0.40
$750
$162
1.0%
3,040
(90)
5
Reduced envelope
leakage to average
(ACH50 = 7.87)
$6,500
$799
5.1%
3,290
197
8
$18,000
$2,298
14.8%
11,619
446
8
Both systems
completely interior
2 central units
(SEER 15)
Electric heat pump
(HSPFc = 8.7)
Programmable
thermostat
16
Measure
Cost
Estimate
Projected
Annual
Cost
Savingsb
Projected
Percent
Savingsb
Projected
Annual
kWh
Savingsb
Projected
Annual
Therms
Savingsb
Simple
Payback
(Years)
$8,661
$1,091
7.0%
28,108
(1,030)
8
$2,000
$1,333
8.6%
12,773
(73)
2
$2,000
$215
1.4%
1,850
–
9
Rework
$2,000
$0
N/A
–
–
N/A
$15,552
$9,777
$45,511
$5,775
37.1%
60,220
(584)
8
111,300
51,080
1,221
1,805
Components
Pre-Retrofit
Proposed Retrofit
Air
Distribution
System
Water
Heating
System
Refrigerator
For heat only; untested;
(R-6; estimated
Qn,out = 0.22)
1, 120-gal electric
(EF = 0.80);
1, 40-gal electric
Multiple commercial grade
1 commercial grade, 8 gas
burners
Replace for heating
and cooling (R-6,
Qn,out = 0.07)
Range
Lighting
T12 and incandescents
Washer and
Dryer
2 sets, electric dryers
Fans
Electrical
Projected
Annual Cost
Projected
Annual kWh
Projected
Annual
Therms
5 ceiling fans, default
efficiency
2 tankless gas
(EF = 0.90)
T8, low-Watt T12,
and CFLsd
Replaced with
ENERGY STAR
a
Assumptions: a 5,800 ft2, block construction; $0.1165/kWh; $2.119/therm
The incremental changes cannot be summed to determine the overall savings. Improvements are interrelated.
c
HSPF = heating seasonal performance factor
d
CFL = compact fluorescent lamp
b
17
Whole-House Infiltration: The window AC units were removed, the penetrations associated with
their removal were sealed, and operational problems were addressed to improve the wholebuilding airtightness. Other measures targeted for leakage reduction included sealing gaps,
cracks, and penetrations to the exterior and applying weather stripping to exterior doors and
frames.
Air pathways between the conditioned space and the commercial kitchen posed a challenge. As
described in Section 2.2, the kitchen was not conditioned, yet not isolated from the rest of the
building, wastefully drawing conditioned air away from the main body during exhaust fan
operation. Researchers recommended isolating the kitchen from the rest of the building and
installing a ductless mini-split to independently condition the kitchen. The contractor agreed to
isolate the kitchen by applying weather stripping to the two interior kitchen doors, but rejected
conditioning the area because of the expense.
Sealing airflow pathways and isolating the kitchen were estimated to reduce the whole-building
leakage to about ACH50 = 8. Given the age and construction of the building, and the limited
extent of the retrofit, post-retrofit airtightness levels were not expected to reach levels that would
suggest a need to implement supplemental mechanical ventilation. The projected annual cost
savings associated with all these building tightening steps was $799, 5.1% of the total annual
cost.
Heating, Cooling, and Air Distribution Systems: The AC and heating systems needed to be
completely replaced. Researcher recommendations were to replace all the window AC units and
the gas furnaces with two forced-air, central heat pumps with a seasonal energy efficiency ratio
(SEER) of 15 and an HSPF of 8.7 or greater. Programmable thermostats were also
recommended.
A complete replacement of the air distribution system with a new system having an R-value of 6
or more was recommended to accommodate the new central heat pumps. Researchers anticipated
duct leakage would be reduced from the pre-retrofit estimate of Qn,out = 0.22 to 0.07 as a result
of the complete mechanical system replacement (McIlvaine 2010). These combined measures
were projected to save $2,298 annually, or 14.8% of the total annual bills.
Water Heating System: Researchers recommended replacing the electric water heating systems
with high-efficiency, natural gas-fueled tankless or electric heat pump water heaters. Given the
building’s excessive water heating demands from 30+ occupants and extensive food services, the
contractor chose high-capacity, natural gas-fueled, tankless units. The subcontractor specified
two units, given the load capacity required to concurrently operate showers, washing machines,
and to allow for the kitchen’s needs. Gas lines and additional plumbing would need to be
installed as a result of the fuel conversion and appliance relocations. The water heating measure
was projected to save $1,091 annually, for a 7% reduction to the total annual cost.
Lighting and Appliances: All light fixtures were slated to be replaced with energy-efficient
lighting products. A high-efficiency replacement for the older of the two washer and dryer sets
was recommended. Researchers specified the washing machine be ENERGY STAR-certified.
The lighting and appliance measures were projected to save $1,333 and $215 respectively, for a
combined total annual cost savings of 10%.
18
Electrical: An update to the building electrical system was deemed essential. This cost was
included as part of the energy efficiency retrofit analysis, because some level of electrical retrofit
was required to change from the gas furnaces to heat pumps.
As presented at the bottom of Table 2, in comparison to the pre-retrofit, weather-normalized,
True-Up pre-retrofit model, electricity use is expected to be reduced by 60,220 kWh annually;
gas use is predicted to rise by 584 therms. The water heating fuel switch is responsible for the
increase in gas consumption. The projected annual energy cost savings from all these measures
was $5,775, a reduction of 37%, which is slightly below the funding program goal of 40%. The
overall simple payback of eight years was longer than the funding program goal of five years.
Although savings and payback projections fell slightly short of the funding program target
metrics, the Beacon House project funding was awarded.
19
4 Characteristics of Post-Retrofit Energy Improvements
In June 2012, researchers visited the Beacon House to interview staff and contractors and to
conduct a post-retrofit audit. The staff reported that they were very pleased with the retrofit.
They also said that the work was done well and very quickly. Contractors worked around Beacon
House staff schedules and did not disrupt the residents or the community. Table 3 provides a
summary of the seven retrofit measures taken. Measure economics are presented in Section 5.1.
The following discussion is a measure-by-measure description of the audit findings.
Table 3. Post-Retrofit Findings by Measurea
Components
Pre-Retrofit
Attic Insulation
Insulated at ceiling (R-1)b
Duct Locations
Windows
Whole-House
Infiltration
Heating and
Cooling System
a
Air Distribution
System
Water Heating
System
Lighting
Washer and Dryer
Electrical
System 1: Supply, return, and
AHU interior;
System 2: Supply attic, return,
and AHU interior
44 single, clear, metal frame (Uvalue = 1.20; SHGC = 0.80
Compromised envelope unable
to depressurize
(estimated ACH50 = 22)
22 window units
(19 @ EER 8; 3 @ EER 9)
2 gas furnaces; 108 kBtu/h
(AFUE 0.71)
No programmable thermostat
For heat only, untested
(R-6; estimated Qn,out = 0.22)
1, 120-gal electric (EF = 0.80);
1, 40-gal electric (EF = 0.80)
T12 and incandescent
2 sets, electric dryers
Assumption: 5,800 ft2, block construction.
Pre-retrofit condition of ~R-7 was determined during retrofit.
c
Washer and dryer set to be replaced after lease expires.
Post-Retrofit
Ceiling insulated to R-34; R-1 for
south 15 ft
Both systems completely interior
Film on first floor south, all east- and
west-facing windows to SHGC ≤ 0.37
Reduced envelope leakage ACH50 to
8.8 (based on ~5,300 ft2)
2 central units (SEER 15)
Electric heat pump (HSPF = 8.7)
Programmable thermostat
Replace for heating and cooling
(R-6; Qn,out = 0.02)
2 tankless gas (EF = 0.82)
T8, low-Watt T12, and CFLs
1 replaced with ENERGY STARc
Rework
b
4.1 Attic Insulation and Duct Locations
With no viable interior attic access, the soffits were removed to allow contractors to blow in
dense pack cellulose. Contractors found that the attic cavity did have some limited insulation,
estimated to be R-7, unlike the R-1 value, which was used for pre-retrofit modeling. New
insulation was blown in over this 2 in. of compressed, blown-in fiberglass insulation. The cavity
depth was not large enough to accommodate an R-38, so an R-value of 34 was achieved. The
unsoffitted, south 15 ft of the building was not accessible and therefore went uninsulated. The
approach of insulating the attic via the soffits was chosen over other methods (insulating from
below via holes in the ceiling) to minimize disruption to the facility, as it remained occupied
20
during the entire retrofit. To reach the soffits, Matrix chose to use a high lift, rather than ladders,
to mitigate the risk of injury. The soffit material was replaced with ½-in. plywood that was
sealed with urethane to create an unvented attic, then primed and painted.
Researchers did not revise the pre-retrofit analysis and true-up based on the contractor’s findings
during the retrofit, because the retrofit scope had already been finalized based on the original
analysis. The effect of incorrect assumptions on the savings analysis is minimized as a result of
the true-up to actual utility data. Lack of access to the attic during the pre-retrofit audit
overestimated the projected savings associated with this measure in three ways:
1. The pre-retrofit assumption was that insulation could be added to the entire ceiling
thermal boundary. However, contractors were unable to access the front 15 ft of the
building’s ceiling, so the presumed post-retrofit improvement greatly exceeded reality.
2. Pre-retrofit modeling assumed attic insulation with an R-value of 1. Observations during
the retrofit suggest that the insulation was nearer an R-7; therefore, the projected
improvement for this measure was overstated by the presumed less-efficient pre-retrofit
condition.
3. Energy auditors assumed that there was adequate attic space to support enough densely
packed cellulose to attain an R-value of 38, whereas only R-34 was possible; therefore,
the projected improvement for this measure overstated the attainable post-retrofit
condition.
4.2 Windows
Window film with a shading coefficient of 0.43 (SHGC ~ 0.37) was applied to the inside of all
but the second floor, south-facing windows, despite the original plan for a more limited
application. Funding to film the additional windows came directly from the Beacon House,
outside the HomeAid grant. The windows that were not filmed are well shaded by deep awnings.
At the time of this report, Matrix reported that it would consider applying film to the remaining
windows as part of an effort to address cooling issues in two offices with untreated windows.
The yet unresolved cooling issue is discussed in Section 4.5.
4.3 Whole House Infiltration
As described in Section 2.3, the removal of the window AC units provided a great opportunity
for whole-house leakage reduction by eliminating the airflow pathways around and through the
equipment. Upon removal, contractors discovered that three windows were not operational,
which the Beacon House gave Matrix permission to permanently seal closed. Although
permanently sealing windows limits egress, it was not an issue with code enforcement. Other
measures taken to reduce whole-house leakage included applying a urethane seal to exterior and
an acrylic seal to interior window penetrations and resealing around window framing, sealing all
visually observed penetrations to the building’s exterior, and sealing the soffits as described in
Section 4.1. Weather stripping was applied to all exterior doors and, in an effort to thermally
isolate the kitchen, to the interior kitchen doors. Post-retrofit blower door test results showed
whole-building leakage to be ACH50 = 8.8. Researchers excluded the kitchen area from the test
because it is well connected to the outdoors, and depressurized the building with the kitchen
doors closed.
21
During the whole-house depressurization test, researchers identified additional leakage sources—
the edges of the attic hatch, around the interior kitchen doors where the weather stripping detail
needed to be readdressed, and an open wall cavity in the second floor air handling unit (AHU)
closet (Figure 13).
Figure 13. Post-retrofit, researchers observed an airflow pathway from a
large open wall cavity between the AHU and the filter grille
4.4 Heating, Cooling, and Air Distribution Systems
Two five-ton SEER 15 HSPF 8.7 forced air, central heat pumps replaced the 22 window AC
units and two gas furnaces, as recommended. The Air Conditioning Contractors Association
standardized Manual J sizing procedure considering post-retrofit specifications was used for
heating and cooling load calculations. Programmable thermostats were installed for each system.
The ground floor AHU is shown in Figure 14. Matrix reported a seamless installation, including
the fuel change, which required capped gas lines. Electrical upgrades were essential to
accommodate the electric resistance backup.
As testament to the effective work done by Matrix and its mechanical contractor, the Beacon
House staff was pleased to see that the AC systems were removed and replaced in one week.
Anecdotally, one semiprivate room resident expressed great pleasure with the more comfortable
environment since the retrofit.
Figure 14. Post-retrofit ground floor, SEER 15 heat pump AHU
22
Although the original retrofit plan included duct replacement, access for installation was limited.
Instead, contractors added a new trunk line to the ducts to allow more return air from the
dormitory room, to balance supply and return air to all spaces and improve comfort. The new R6 insulated return run was attached with mesh and mastic and installed between floors and into
penetrations made in the internal block walls. Previous renovations in the ceiling restricted
access to some areas of the building and structural degradation from termite damage created a
retrofit challenge of limited options to locate duct runs.
After HVAC upgrades staff reported that the two second-floor offices were still not cooling
adequately. Undoubtedly, this was in part due to the lack of ceiling insulation above these rooms
(see Section 4.1) and the high occupancy level. Access to the duct servicing this section of the
building was limited and not economically feasible. During the post-retrofit audit, researchers
tested the room pressures with respect to the main body while the mechanical system was
running and found these two offices to be slightly positively pressurized (1 and 0.9 Pa).
However, the large dormitory, serviced by the same supply line just before these offices, was
positive 6.2 Pa. Researchers recommended that contractors reduce the amount of conditioned air
being delivered to the dormitory to make it less positively pressurized and force more
conditioned air into the problem rooms. Further, researchers recommended return air pathways
be installed in the front offices and the semiprivate rooms to help balance pressures and
temperatures throughout the building. As of the time of this report, contractors had restricted the
amount of air being delivered to the dormitory, but this was not sufficient to provide adequate
comfort to the offices. Matrix was continuing the investigation to correct the issue and
considering installing new supply duct lines to these rooms.
Post-retrofit duct leakage tests revealed the retrofitted duct system to be essentially devoid of
leakage to the outside. The large penetration between the return plenum duct board and the wall
cavity in the second-floor AHU closet was masked during duct testing (Figure 15). Matrix
agreed to seal this access; however, masking this area for testing may have yielded better results
than the eventual state. The first floor system duct leakage test results were Qn,out = 0.006, and
the second floor system test results were Qn,out = 0.03. The combined results of the mechanical
system change-outs and the duct retrofit yielded a significantly reduced duct leakage from the
assumed pre-retrofit condition of Qn,out = 0.22.
4.5 Water Heating System
Two externally mounted, natural gas water heaters (Figure 15) replaced the three electric tank
units. This was an expensive retrofit measure because the gas piping servicing the building
needed to be upgraded and water lines rerun to accommodate the new water heater locations. The
EF for the new water heaters was 0.82, less efficient than the 0.90 recommendation. Matrix
indicated the priority was finding equipment with the highest available capacity to accommodate
the facility’s large water heating demands.
23
Figure 15. Two externally mounted gas tankless water heaters
4.6 Lighting and Appliances
The lighting retrofit was incomplete during the post-retrofit audit, but complete replacement of
all light fixtures with energy-efficient lighting products was being completed as proposed. This
includes exchange of all incandescent light bulbs with compact fluorescent lamps (CFLs) in the
bedrooms, some bathrooms, the laundry room, and two of the offices; 40-W T8 linear
fluorescent tubes in the heavily used kitchen, kitchen hall area, and kitchen storage areas; and
34-W T12 linear fluorescent tubes throughout the remainder of the building.
Though one clothes washer and dryer set was slated for immediate replacement, Matrix
discovered that the units were being leased by Beacon House for another year. For this study,
researchers assumed the eventual purchase of efficient appliances, including an ENERGY
STAR-certified washing machine.
24
5 Post-Retrofit Energy Cost Savings and Cost Effectiveness
Once the post-retrofit energy audit was completed, researchers recreated the energy use
simulation in EGUSA reflecting the actual post-retrofit findings and test results. Simulation
savings projections are accompanied by pre-retrofit cost estimates provided by Matrix. The
Beacon House retrofit economics are provided in Table 4, which is a lateral extension of Table 3
in Section 4. This table provides the same metrics provided in Table 2 (measure cost, projected
annual cost savings, projected percent savings, projected annual kWh and therms savings, and
simple payback) and discussed in Section 3.4, in addition to an SIR for each measure. SIR
calculations are those recently adopted by RESENT (RESNET 2012). For this analysis, a sevenyear mortgage period was assumed. See the Appendix for all SIR calculation assumptions.
Incremental costs are sometimes used for evaluating cost effectiveness when a higher efficiency
specification is selected for replacement of an item at the end of its life. As a prime example,
assuming an air conditioner is at the end of its life, the incremental cost for installing a highefficiency system is the cost difference between the chosen unit and the least costly system
available. Simple payback can be considerably shortened when considering only incremental
costs. Although some of the Beacon House building components and appliances appeared to be
operating beyond their useful lives, the metrics established by the funding organization address
full costs only and incremental costs were not used in that analysis. However, researchers
considered first costs and incremental costs in the SIR calculations for appropriate Beacon House
retrofit measures.
25
Table 4. Post-Retrofit Measure and Package Costs and Savingsa
Components
Attic Insulation
Duct Locations
Windows
Whole-House
Infiltration
Heating and
Cooling System
Air
Distribution
System
Water Heating
System
Lighting
Washer and
Dryer
Electrical
Projected
Annual Cost
Projected
Annual kWh
Projected
Annual Therms
a
Measure
Cost
Projected
Annual
Cost
Savings
Projected
Percent
Savings
Projected
Annual
kWh
Savings
Projected
Annual
Therms
Savings
Simple
Payback
(Years)
SIR
$5,600
$228
1.5%
890
59
25
0.44
$750
$188
1.2%
3,000
(75)
4
2.08
$6,500
$739
4.8%
2,900
185
9
1.18
$18,000
$2,530
16.3%
13,614
446
Fullb: 7
Incb: 1
Full: 1.15
Inc: 5.93
2 tankless gas (EF = 0.82)
$8,661
$875
5.6%
28,108
(1,131)
10
0.57
T8, low-Watt T12, and CFLs
1 replaced with
ENERGY STARc
Rework
$2,000
$1,333
8.6%
12,773
(73)
2
2.95
$2,000
$215
1.4%
1,850
–
9
0.88
$2,000
$0
N/A
–
–
N/A
$10,177
$45,511
$5,375
34.6%
58,626
(685)
8
N/A
Full: 0.91
Inc: 1.29
Post-Retrofit
Ceiling insulated to R-34; R-1 for
south 15 ft
Both systems completely interior
Film on first floor south; all eastand west-facing to SHGC ≤ 0.37
Reduced envelope leakage ACH50
to 8.8 (based on ~5,800 ft2)
2 central units (SEER 15)
Electric heat pump (HSPF = 8.7)
Programmable thermostat
Replace for heating and cooling (R6; Qn,out = 0.02)
52,674
1,906
2
Assumptions: 5,800 ft ; block construction; $0.1165/kWh; $2.119/therm
Full assumes the full cost of the replacement. Inc assumes the incremental cost above a SEER 13 straight cool, estimated to be $1,150 for each system. Added
to this cost is $100 per programmable thermostat and $1,000 for the ductwork retrofit, for a total of $3,500. Electrical rework is incorporated into the total SIR.
c
One washer and dryer set is to be replaced after the lease expires. Lease expense was not factored into savings or SIR.
b
26
5.1 Measure Cost Savings and Cost Effectiveness
Attic Insulation and Duct Locations: Annual energy cost savings associated with the attic
insulation and soffit sealing measure is projected to be $228 annually, or 1.5% of the total annual
utility costs. This measure comes with a lengthy simple payback of 25 years. Looking to break
even between cost and benefit, an SIR value of 1.0 or higher is desired for each measure,
meaning the present day value of savings is at least equal to its cost. With an SIR of 0.44, the
insulation and duct location measure fails this metric. Had the contractor been able to access the
front 15 ft of the building’s attic, break-even cost would have easily been achieved.
Windows: Because more windows were filmed than planned, the proposed projected annual
energy cost savings associated with the window film measure was slightly exceeded. This
measure saves $188 annually, or 1.2% of the total annual utility costs. The simple payback for
this measure is just four years. Although the measure provides only small energy cost savings,
with an SIR of 2.08, it is a valuable part of the retrofit package.
Whole-House Infiltration: Projected energy cost savings associated with the infiltration reduction
is $739, 4.8% of total annual energy costs. This measure has a projected simple payback of nine
years. Although the cost for these air sealing measures was high, great savings are projected
driving the SIR above break-even cost, to 1.18.
Heating, Cooling, and Air Distribution Systems: Projected annual energy cost savings of the
entire heating and cooling system upgrade, which included installation of programmable
thermostats, is $2,530, 16.3% of the total annual utility costs. The combined simple payback for
these measures is seven years. An SIR of 1.15 narrowly surpasses break-even. Yet, arguably only
incremental costs should be included in the SIR calculation because the pre-retrofit systems did
not adequately provide comfort to the occupants. Assuming only incremental costs from SEER
13 straight-cool resistance heat systems to SEER 15 heat pumps, plus the cost of two
programmable thermostats and the ductwork retrofit, researchers estimate a much higher SIR of
5.93 and a simple payback of one year. These projections are weakened, however, by the
unknown pre-retrofit duct condition and location.
Such low post-retrofit leakage on distribution systems that were not entirely replaced put into
question the pre-retrofit leakage assumption of Qn,out = 0.22. However, even with the
centralized control, a cooling set point of 72°F was observed during the post-retrofit audit. This
temperature is 10°F cooler than the set point estimated for the pre-retrofit condition through the
true-up exercise (see Section 3.3). Although the 82°F pre-retrofit set point was used to true-up
estimated cooling energy use rather than to reflect an actual condition, the observed post-retrofit
set point is certainly expected to diminish the projected savings. To counteract this, training has
been recommended to educate staff on the effect of set point on space conditionoing energy use.
For every degree the thermostat is lowered during the cooling season, a 10% increase in cooling
energy can be expected.
Water Heating System: The tankless gas water heaters are projected to save $875 annually, a
5.6% reduction in total annual energy costs, and the simple payback is 10 years. Installation costs
included a fuel conversion and new plumbing lines, essentially doubling the cost of this measure.
As a result, the SIR is 0.57, well below break-even for this metric. Although the existing units
27
were older, all were in working condition. Thus, an SIR based on incremental costs was not
calculated.
Lighting and Appliances: The lighting retrofit is projected to save $1,333 annually, 8.6% of the
total annual energy costs. The expected payback is just two years, and the SIR of 2.95
demonstrates great value. Replacing the leased washer and dryer with the new purchase is
projected to save $215 annually, or 1.4% of total energy costs. Researchers project a nine-year
simple payback. An SIR calculation with incremental cost is not appropriate because the old
equipment was leased. The lease fee is one half of the revenue generated by these coin-operated
machines. For the purposes of this SIR calculation, researchers treated the appliances as if they
were owned.
5.2 Summary of Cost Effectiveness
As presented at the bottom of Table 4, in comparison to the pre-retrofit weather-normalized
True-Up model, the projected annual energy cost savings expected from the Beacon House
retrofit is nearly 35%, with projected savings of $5,375. The anticipated simple payback is eight
years. Electricity use is expected to be reduced by 58,626 kWh annually; the projected gas use
will rise because of the fuel switch to natural gas water heating. The overall savings falls just
short of the funding program goal of 40% savings and a five-year simple payback. Including the
costs for the electrical upgrade, the cumulative SIR for the retrofit package assuming all full
improvement costs is 0.91. Adjusting for incremental costs (HVAC), the cumulative SIR rises
above break-even to 1.29.
Savings were lost because the attic could be insulated only to an R-value of 34, where it was
accessible, and much of it was inaccessible. Strictly regarding SIR, the only measures for
consideration in an optimization analysis would have been the window tinting, building air
sealing, the mechanical system change-out, the lighting retrofit, and the replacement of the
washer and dryer (assuming a small lease cost savings). The attic insulation measure would have
been a much stronger contender if the building design had allowed this measure to be
implemented as expected, which would have been the case if the water heater installation had not
required fuel conversion and new plumbing lines.
28
6 Conclusions
Overall, the Beacon House retrofit successfully addressed energy use, comfort, and durability
and met the general goals of the residents, staff, and funding agency. The utility data-backed,
weather-normalized True-Up model clearly provided researchers a better baseline to project
energy savings for this retrofit than the initial model created with software defaults for a
residential building. The regression model using monthly HDD and CDD to suggest monthly
energy use had the building been subjected to TMY3 weather provided strong, predictive values.
This allowed researchers to disaggregate heating and cooling loads from base loads, a powerful
piece of the true-up simulation effort. However, this true-up method was unable to disaggregate
71% of electricity end uses.
Obstacles were presented in evaluating energy use in a building with these architectural and
operational characteristics. Energy cost savings projections were hampered by imperfect
knowledge of the pre-retrofit condition. As presented in Section 4.1, understating the energy
efficiencies for baseline model components produced overestimates in the energy cost savings
for related measures. Savings projections for some measures were overstated because the
knowledge about the building was limited due to the limited pre-retrofit audit. The attic
insulation and the mechanical distribution system were affected by this. Energy cost savings
projections were weakened by unknown pre-retrofit duct leakage and whole-building
airtightness, as highlighted in Sections 2.2 and 2.3.
Difficulties were presented in retrofitting a transitional housing building with these architectural
characteristics and of this vintage. Some age-related and architectural obstacles created
unforeseen costs and effectively limited some measures. The building displayed signs of multiple
renovations performed over the years that limited access to some areas of the building. Termite
damage led to structural degradation of the building. Therefore, it was necessary to add wood for
structural stability. These realities impacted the mechanical system replacement, limited the attic
insulation measure, and ruled out a potential window retrofit and a mechanical ventilation
strategy, as discussed in Sections 4.4, 4.1, and 3.4, respectively.
The kitchen presented another difficulty. The contractor thought the overall retrofit would have
been more effective had the comfort in that room been addressed. Although creating an air
barrier between the kitchen and the rest of the building was a logical design because of the large
exhaust draws ingrained in a commercial kitchen, a preferable solution would have included
independently conditioning the space with a ductless mini-split. The kitchen would still
experience some energy loss through the exhaust vents regardless of where the space
conditioning came from, however. Budgetary constraints meant that it was not technically
possible to create adequate living space comfort in the kitchen. Further, workers did not seem
bothered by the warm working environment.
Overall, the projected energy cost savings expected from the Beacon House retrofit are nearly
35%; annual savings are projected to be $5,375. A simple payback is eight years. Though the
retrofit did not precisely follow the proposed package, the overall savings project roughly
matches the initial pre-retrofit projections of 37% reduction in energy costs for $5,775 annual
savings with an eight-year payback. In terms of measures that provide the best projected energy
cost savings and SIRs for this facility (see Section 5.1), the expected savings from the
29
mechanical system upgrade, 16.3%, represents almost half the entire project savings projected.
Other noteworthy measures are the lighting retrofit, installation of tankless gas water heaters, and
improved whole-building airtightness, which are projected to save 8.6%, 5.6%, and 4.8%
respectively. Considering the full costs involved with each measure, the best measures to
consider are the lighting retrofit and the window film measure with SIRs of 2.95 and 2.08,
respectively. However, when examining incremental costs where appropriate, the mechanical
system upgrade provides the best economics with an SIR of 5.93.
Not surprisingly, the project considers the removal and replacement of the heating and cooling
systems to be the most successful measure. In addition to the improved mechanical efficiency,
the building now has balanced airflow. Removing the window units also provided opportunities
for restricting uncontrolled airflow into and out of the building.
The next logical step would be to confirm energy cost savings. Researchers anticipate actual
savings to be greatly influenced by the fluctuation between pre- and post-retrofit occupancy
behavior, but not necessarily because the rapid turnover in residents means the pool of postretrofit occupants will be composed substantially of different people, because with 30 residents,
perhaps this variation would average out. In the post-retrofit condition, staff has greater control
over operational settings. However, observations show that even with greater staff control, postretrofit energy consumption may be influenced by the take-back effect. Granted additional
funding, additional research to address these questions could include monitoring indoor air
temperature and relative humidity, recording set points, and surveying occupants.
30
References
Brozyna, K. (2012). Results from Development of Model Specifications for Multifamily Energy
Retrofits. NREL/SR-5500-53624. Work performed by Integrated Building and Construction
Solutions (IBACOS), Pittsburg, PA. Golden, CO: National Renewable Energy Laboratory. Accessed
2012: http://www.nrel.gov/docs/fy12osti/53624.pdf
Florida Solar Energy Center. (1996-2005). EGUSA. Accessed 2012:
http://www.energygauge.com/usares/.
“Industry Statistics Sampler: NAICS 624221 Temporary Shelters.” U.S. Census Bureau, 2002.
Accessed 2012: http://www.census.gov/econ/industry/hist/h624221.htm
McIlvaine, J.; Sutherland, K.; Schleith, K.; Chandra, S. (2010). “Exploring Cost-Effective, High
Performance Residential Retrofits for Affordable Housing in the Hot Humid Climate.”
Seventeenth Symposium on Improving Building Systems in Hot and Humid Climates;
August 24–26, 2010, Austin, TX.
“Residential Finance Survey 2001: Census 2000 Special Reports.” U.S. Census Bureau, 2005:
Accessed 2012: http://www.census.gov/housing/rfs/data/censr-27.pdf
RESNET. (2012). Mortgage Industry National Home Energy Rating Systems Standards, Section
303.3.3 Economic Cost Effectiveness. Oceanside, CA: Residential Energy Services Network.
Accessed 2012: http://www.resnet.us/standards/mortgage
31
Appendix: SIR Calculation Assumptions
Economic Parameters
General Inflation Rate
Discount Rate
Mortgage Interest Rate
Down Payment Rate
Energy Inflation Rate
Analysis Period (Years)
Mortgage Period (Years)
Values
Measures
Attic Insulation
Window Tint
Infiltration Reduction
Useful Life (Years)
40
15
30
Heating & Cooling System1
Water Heating System
Lighting
Washer & Dryer
1
2.39%
4.39%
6.15%
10.00%
4.42%
30
7
15
12
5
15
The SIR calculation for this measure includes the distribution system changes. An assumed 15-year
useful life was used for all elements of this combined.
32
DOE/GO-102013-3853 ▪ February 2013
Printed with a renewable-source ink on paper containing at
least 50% wastepaper, including 10% post-consumer waste.